the applications by relieving them from the need to perform the mixing of audio streams, especially on low-end sound cards that didn't support multiple sound streams. However, it introduced some significant problems. First, the latency of KMixer is around 30 ms and it cannot be reduced, because this component sits just right above the port class audio driver, so every audio stream, including those issued by DirectSound (except in cases of hardware mixing) and WinMM, come through the kernel mixer. If the audio hardware supports hardware mixing (also known as hardware buffering or DirectSound hardware acceleration), DirectSound buffers directly to the rendering device. Thus, if DirectSound streams use hardware mixing, KMixer is bypassed. In earlier releases like the original release of Windows 98, KMixer tried to mix every data format that passed through it, even those it did not support. It caused various problems with media players that tried to pass AC3-encoded surround sound streams through S/PDIF output of the sound card to an external home cinema receiver. This was corrected with Windows Me and provided as a hotfix for Windows 98 Second Edition and Windows 2000 SP2. Starting with Windows Me, the , DirectSound, and DirectShow APIs support non-PCM formats such as AC-3 or WMA over S/PDIF and non-PCM data goes directly to the class driver instead of going through KMixer. A new kernel-mode API, Direct Kernel Streaming, was also introduced in Windows 98 in order to bypass the KMixer and avoid problems associated with it. KMixer does not alter the sound in the majority of cases. Also, there are many ways to bypass KMixer without the need of an extra plugin to access DirectSound, ASIO, Direct Kernel Streaming or WASAPI. In Windows XP, for example, the usage of DirectSound (which Winamp uses by default) with a hardware mixer is a way to bypass KMixer. KMixer was removed in Windows Vista. It is replaced by the user-mode WASAPI (Windows Audio Session API) Audio Engine which is part of the revamped audio architecture. The Audio engine can operate in Shared mode or Exclusive mode. In shared mode, mixing still takes place. Pre-mixed PCM audio is sent to the driver in a single format (in terms of sample rate, bit depth and channel count) that is configurable from the Sounds control panel. WASAPI Exclusive mode bypasses the mixer, as does using third-party audio APIs like OpenAL or ASIO, which still have